The present invention relates to a process and a device of elemental analysis of the Carbon, Hydrogen, Nitrogen, and Sulfur content by means of flash combustion in oxygen and for the analysis of the Oxygen content by means of pyrolysis.
Various processes for elemental analysis by means of xe2x80x9cflash combustionxe2x80x9d of the sample are known. This technique provides for the introduction of the sample into a heated reactor vessel in the presence of oxygen so as to cause substantially instantaneous combustion of the same; the gases released are then analyzed. Generally, the sample is housed in a tin (Sn) container.
One known process of analysis (used by LECO(copyright)-USA) provides for operation in a continuous flow of oxygen. The resulting gases are treated to ensure all combustion is complete and sent to a mixing tank where only a part is then analyzed. The main drawback of this solution is the large quantity of oxygen consumed; furthermore, the step of removal of a part of the combustion gases is a possible source of problems.
European Patent Application N. 0586969, In the name of the present applicant describes an elemental analysis process to determine the total nitrogen content. According to this document, the flash combustion is carried out in a flow of helium, with the necessary oxygen being supplied from a loop. The loop must be kept constantly full, with consequent consumption of oxygen; furthermore the quantity of sample which can be analyzed depends on the volume of the oxygen loop.
An aim of the present invention is to avoid the aforementioned drawbacks, and provide a process for elemental analysis which is flexible and inexpensive, which reduces the volume of oxygen consumed to a minimum, and which can be applied without problems to samples varying widely in weight and substance.
It also is an aim of this invention to provide a device to carry out the above process.
Namely, the present invention relates to a process for elemental analysis by means of flash combustion, characterized by comprising the following steps: determining the volume of oxygen required for the analysis of the sample by means of the following algorithm:
Qo=xcex94(Qc)xe2x80x83xe2x80x83[1]
where:
Qo is the volume of oxygen required, Qc is the weight of the sample to be analyzed and xcex94=Qo1/Qc1 
where Qo1 is the volume of oxygen necessary for the combustion of a predetermined quantity Qc1 of the sample to be analyzed;
pulse-feeding the said volume of oxygen Qo to the said combustion reactor from a source of oxygen, by means of a flow regulator.
According to a preferred aspect of the invention, the value xcex94 is determined experimentally for each type or class of sample in relation to their nature, and memorized in a means of retrieval and processing for use in the analysis.
According to a further aspect of the invention, the volume of oxygen required Qo1 is determined by measuring the time Tc required for the complete combustion of said pre-determined quantity of sample Qc1. The flow-rate P of the oxygen fed to combustion reactor is measured, and the said value Tc is multiplied by the said value P.
The invention relates furthermore to a device for flash elemental analysis, comprising a combustion reactor, means for supplying a flow of inert carrier to the device, a source of oxygen and a feed line for feeding oxygen to said reactor, a flow regulator on said feed line of oxygen, and means of determining the volume of oxygen required for analysis of the sample by means of the following algorithm
xe2x80x83Qo=xcex94(Qc)xe2x80x83xe2x80x83[1]
where Qo is the volume of oxygen required, Qc is the weight of the sample to be analyzed and xcex94=Qo1/Qc1, and where Qo1 is the volume, known and measured, of oxygen necessary for the combustion of known quantity Qc1 of the sample to be analyzed.
According to a preferential aspect of the invention, the device furthermore comprises a means of memorization and electronic processing in order to: memorize a plurality of constants xcex94 for a corresponding plurality of types of sample; memorize the algorithm [1]; receive the data related to the type and quantity of sample to be analyzed and calculate the said volume of oxygen Qo required for each analysis.
The invention has numerous advantages compared to the present state of the art. The advantages are of an economic, analytical and practical nature. The process of the invention allows the use of only that quantity of oxygen necessary to completely burn the sample, in slight excess. The daily consumption of oxygen for analyses has been found to be about one tenth of the consumption which would be used by traditional oxygen loop systems of analysis. A further advantage is that, as well as saving oxygen, there is also saving on reduced copperxe2x80x94necessary to reduce oxidesxe2x80x94which now lasts longer. In practice it is possible to at least double the number of analyses obtained for the same quantity of reduced Cu used, compared to oxygen loop analysis.
The analytical advantages result from the greater efficiency of the copper which, not having to treat large quantities of analytical oxygen, remains unaltered over time.
From a practical point of view, the various xcex94 have been established experimentally for a large number of samples of diverse type and nature and are memorized in a processor in the production step of the device. At the moment of analysis, the operator is only required to set the type and the weight of sample to obtain automatic delivery of the quantity of oxygen necessary to burn the sample. Only where the type of sample to be analyzed is not among those in memory or where the nature of the sample is unknown, does the operator proceed to establish the xcex94 and memorize it.